Primitive Obsession – The code smell

Programming languages divide their types mainly into two categories.

  • Primitive types (A built-in types like string, boolean, int, decimal…)
  • Objects (class/function): User-defined types using class-based/prototype-based objects.

A primitive data type is a data type for which the programming language provides built-in support. Example: number, string, boolean, date and so on.

There are situations when developers should represent their idea/concept using user-defined types (Abstraction or encapsulation).

Whereas they choose to use primitive types (inbuilt int, string…) to represents the concept.

“Talk is cheap. Show me the code.” ― Linus Torvalds

Consider the above API for scheduling meetup.

If you observe carefully, all the parameters: topic, description, date, location id, and max participants when they stand together represent the concept/idea called meetup.

Almost all the data types are primitive types (Built-in types: string, int, DateTime and so on).


Overutilization of these primitive types to solve a problem makes the code more verbose/procedural and logic to deal with them is scattered.


Since all method parameter stands together to represent the concept called Meetup.

Here, we could group all these parameters together to represent the idea/concept called meetup. So, introduce an object to gather these data values.

Upon replacing data values with an object API would look like:

This is how the API should have been. However, the developer chooses to go with all built-in types (segregated). IMO, this overutilization of primitive types in almost all cases can be treated as an obsession about primitives which can be called a primitive obsession.

I have explained only one scenario and there are other scenarios too.

Test case structure

A commonly applied structure for test cases has

  • Setup: Arrange the state of the unit under test in order to run the test.
  • Execution: Act on the unit under test so that it performs the expected behavior and receive output if needed.
  • Validation: Assert/Verify the outcome of execution.
  • Cleanup: Restore unit under test to a pre-test state.

Test-driven development benefits

  • Design first: You understand requirement first via analysis, create use cases for it. Thus, the focus is on the requirement before writing the code.
  • Good enough code for now: You write sufficient code against use cases that fulfills the user requirements. You don’t write extra lines of unnecessary code.
  • Avoid rework: Due to design first approach, most of the doubts are cleared before writing code hence rework is avoided.
  • Developer confidence: Continous delivery of requirement in small cycles gives developer a confidence.
  • Regression catching.
  • Safe Refactoring: Once the code is covered by multiple tests, a developer can safely improve code structure with confidence and can focus on simple and elegant design.
  • A shared understanding of the business: Tests are the live documentation that is the communication channel between you and your future version or other developers that talks about business rules.
  • Clean code reminder: IMO, TDD always reminds you to make your code better than you found it. Of course, after covering your code with test, make it better.

Rest parameter under the hood…

You know the rest parameter (usually prefixed with ...) allows functions or methods to accept indefinite numbers of parameters.

This parameter is actually gathering the values from arguments and creates an array of values from it.

How? Let’s see with code using ES6 rest parameter and it’s corresponding transpiled version.

Simple snippet with rest parameter

First snippet: The function with Rest parameter ‘…days’

Obviously, line 2 will print an array:

[ 'Monday', 'Tuesday', 'Wednesday' ].

You wonder, How it’s an array? Let’s inspect it via transpiled version.

Below code is transpiled using BABEL.

Transpiled version:

Transpiled version of first code snippet. The days variable is initialised as an array and copies element from argument object.

Under the hood, the rest parameters are actually derived from arguments object of called function, `print`. Please notice carefully variable days on line# 5.

It’s value is set to an array whose length is equal to number of arguments passed.

Later, elements from arguments are copied to variable days (element by element from line# 8 to 10).

Another Example

Second snippet

In the second code snippet, please note there is a parameter multiplier apart from rest parameter ...numbers. Hence, copying will not begin from first element instead it started from second element till last one.

See transpiled version for more details.

Transpiled version

Transpiled version of second snippet. Please note argument objects first element is skipped.

const does not mean value it holds is immutable

I see many JavaScript developers have started replacing var with const just because some linter forces them to do so.

const in JavaScript is not only blocked scope but also const variable cannot be reassigned with new content.

It creates readonly reference. It means you cannot reassign value to the const variable. It does not guarantees immutability of the content that it holds.

const person = { name: 'John Doe', age: 33};
person = { name: 'John'} 
// Above line will throw Uncaught TypeError: 
// Assignment to constant variable.

// However, you can change the content of object
// that is referenced by person variable.
person.age = 40;  

So, If you really want to mark your object as immutable then use some other API’s like `Object.freeze`.

There are specific use cases about const variable. Make sure you are intentionally marking some variable as const and not because some linter has that rule.

Fizz-Buzz generator using test driven development

Photo by Kevin Grieve on Unsplash

This is a Fizz Buzz generator using test driven development.

Problem statement:

The Fizz buzz generator is a simple program, it’s method say generate accepts the numeric input and produces the output string based on the rules and input number.


The generate method returns the string

  • FizzBuzz when input parameter is divisible by 3 and 5.
  • Fizz when input parameter is divisible by 3.
  • Buzz when input parameter is divisible by 5.
  • String representation of given number when input parameter neither divisible by 3 or 5.

It is clear that there are four use cases to implement

  • FizzBuzz As a fizz buzz generator, I should be able to generate a string FizzBuzz for a given input number when the number is divisible by 3 and 5.
  • Fizz As a fizz buzz generator, I should be able to generate a string Fizz for a given input number when the number is divisible by 3.
  • Buzz As a fizz buzz generator, I should be able to generate a string Buzz for a given input number when the number is divisible by 5.
  • Number (converted to stringAs a fizz buzz generator, I should be able to generate a string format of input number for a given input number when number is neither divisible by 3 or 5.

Visit the github repository fizz-buzz-generator for TDD implementation.

Don’t forget to go through commit by commit to witness the test driven development journey.

Naming query variables

After working with the different framework and libraries like Laravel, PHP, ASP.NET MVC, ExpressJS and other technologies, I realized that I should write about naming query variables. Perhaps, variable that holds the query and executes it later (Deferred execution).

Sometimes, when developers of any language or framework choose to write the query that gets data using deferred execution, they don’t include the word “query” in the variable name.

Due to exclusion of word `query` in such a variable name, the maintenance developer presumes that the query will be executed immediately. This assumption leads them to introduce bugs in their code.

Please ensure to include the word `query` in the variable name so that it conveys the reader that it is NOT to be executed immediately.

As always, we have to provide meaningful and intuitive names to query variables. See some of the examples below:

Naming query variable examples

  • puneCustomersQuery: When I want to fetch the customers in Pune locations.
  • allPackagesQuery: When I want to fetch all the packages.
  • evenNumberQuery When I want to fetch even numbers from a given data source.
  • damagedPackagesQuery: When I want to fetch packages that are marked as damaged.
  • customersByCityQuery: When I want to fetch customers that are grouped by their city.
  • customerNameQuery: When I want to fetch customer names from a given data source.
  • soldOutProductsQuery: When you are fetching the sold-out products.

Be declarative wherever possible

Imperative programming focuses on describing how a program operates. Take an example of the below function “ isPresent “.

First example: Imperative way, Look implementation of isPresent function.

Of course, it searches a number (search term) in the numbers array and replies with true or false.

If you observe carefully, it focuses on how the number is searched.

It iterates each number one by one in an array of numbers and checks if criteria are fulfilled (HOW part: for/if). Eventually, it tells you if the number is present/not in the array.

Declarative programming, on the other hand, expresses the logic of a computation without describing its control flow.

Let’s look at the declarative way of searching a number in an array.

Declarative way: Any function from LINQ.

In the above code, the method Any (present on array data type), is an extension method provided by LINQ.

It determines whether any element of a sequence contains a given number. It does not tell you how it is searched. That part is hidden behind API: Any.

The benefit of a declarative approach over the imperative approach is improved readability of code.

Another example:

Second example: Imperative way. See containsAllMen function: focuses on describing how a program operates (Control flows are involved: iterate and if)

This function “ containsAllMen “ tells you how searching is implemented and control flow like if clause determine the condition.

Now see the declarative way, it is using lodash’s every to determine the condition.

The declarative way: Using every function from lodash.

This technique is language agnostic.

You search libraries that do such work for you instead of implementing it by yourself.

Naming functions or methods

Photo by Markus Spiske on Unsplash

I will show you bad and good naming of methods with the help of some code examples. Let’s see some of the typical functions related code smells on a case by case basis.

Smells —


  • appointCR(…) : What does CR mean? Appoint code reviewer or class responsible? It was about appointing a class responsible role to a teacher. Hence rename it to appointClassResponsible()
  • cb = function () { … } // CB?? callback.
  • handleClk() : This one is supposed to handle Clicked. So, why not rename it to handleClicked, onSaveClicked, onSave or onUpdate?
  • rand() { return Math.floor(Math.random() * 1000)
    : rand doesn’t seems to be a method from outside. getRandomNumber() seems okay to me.

Not doing what it says

  • changePage(url){ this.props.history.push(url); }
    It was actually nativagating to given url, so, I would rename it to navigateTo(url)?
  • validationErrors()
    It was doing student validation. The Name doesn’t tell you anything. I would rename it to validateStudent()?

Use of nouns instead of verbs in method names

  • jwtAuthentication()
    – I would rename it to a verb like authenticate()
  • jwtTokenDecryption()
    – I would rename it to a verb like decryptToken()
  • jwtTokenValidation()
    – I would rename it to a verb like validateToken()
  • categoryOptions() 
    – I would Rename it to a verb like getCategoryOptions()

Noisy words

  • getAppointmentInfo()
  • getAppointmentDetails()
  • getAppointmentInformation()

Why are you adding noisy/redundant words like Info, Details, Information in front of appointment? In my opinion, getAppointment() gives us information about the appointment. Keep it simple.


  • getStudentsList()
  • getStudentsCollection()
  • getStudentsArray()

Just getStudents() make sense to me. You don’t need to tell your audience about how’s your implementation under the hood.

Not symmetric

  • turnOn()/disable()
  • openConnection()/shutConnection()
  • increaseVolume()/turndownVolume()

If you are adding symmetric methods, then make sure they feel symmetric one.

  • turnOn()/turnOff()
  • openConnection()/closeConnection()
  • readFile()/writeFile()
  • increaseVolume()/decreaseVolume()

Not having descriptive/searchable names

  • booleanValue(value)?? Oh! After browsing the code, I realized that it was converting the string value to boolean. I would rename it to toBoolean(value)
  • deactivate() :It was deactivating the membership. I would rename it to deactivateMembership()
  • invoke(): It was invoking a controller’s action. I would rename it to invokeAction().
  • disable(): Disable what? Authorization? I would rename it to disableAuthorization().
  • handle(): Handling what? Handling subscription? I would rename it to handleSubscription().

One word per concept

  • fetchActiveStudents()
  • retrieveActiveStudents()
  • getActiveStudents()

Why are you using different words (fetch, retrieve, get) for the same concept? Just choose one word per concept and use it throughout your project.

  • getActiveStudents()
  • getPackages()
  • getAppointments()

Side effects

  • ValidateToken() should NOT create a token. I would take `create token` logic out of the method. It’s a side effect.
  • getValue(key, callbackForCreate) should not create value for a given key. Sometimes, people try to get a value from the cache for a
    given key. If the value is absent then they try to create value inside the cache using a given callback function. I would separate these concerns into different functions. Read more about command query separation.
  • createUser() — This method was doing multiple things. It was validating user inputs, creating a user, sending registration email using asynchronous operation. This method seems like registerUser() and it should outsource the responsibilities to validateUser(), createUser() that stores a record and sendEmailAsync() method that conveys that email would be sent later. 

    If you are not going to refactor it into three new methods due to the deadline, then at least rename it to registerUserAndSendEmail()

Look for anti-patterns:`And`, `Or`, `If`.

  • createUserAndSignToken()
    If a method contains keywords like And, Or, If in its name, it’s an indication that the method is doing more than one thing, which is a violation of the Single Responsibility Principle.

Command and query in one function

  • fetchAndSaveCategoryDetails() method is not just doing more than one thing, but also executing command and query in one function. The best thing is to simply separate command and query. Create separate functions. fetchCategory() and saveCategory().

The guidelines for naming methods:

  • The function should be cohesive. The function should say what you mean. The consumer of the function should not browse your function to see what it is doing.
  • Separate command and query: Create a separate function for command and query. Here, command means to save, update, delete the records and query means all get or list methods like getStudent(id), getActiveStudents() etc.
  • Explore open source projects for your technologies and explore how names are given. I explored many JavaScript libraries, Lavavel PHP source code, .NET source code: